This application relates to an apparatus for use in vacuum assemblies and, more particularly, to an apparatus for stoppering sample vials while under vacuum.
It is often desirable to retain samples of material in discrete containers under vacuum for storage. A plurality of these discrete containers may be placed under vacuum in, for example, a desiccator and stored in such manner. However, without elaborate mechanisms for stoppering the individual vials, such as may be found in freeze drying apparatus, particularly those disclosed in U.S. Pat. No. 3,448,556 and in the Freeze Dryer Stoppering Apparatus, Application Ser. No. 832,786, filed Sept. 12, 1977, samples stored under vacuum in an open vial can be cross-contaminated by an adjacent vial or by impurities in the system. The above art each teaches a means for stoppering a plurality of vials within a freeze drying apparatus by the upward movement of an entire shelf against the flat bottom surface of the shelf above. An alternative approach, using inflatable bellows to stopper the vials as taught in U.S. Pat. Nos. 3,795,986 and 3,022,619, is not entirely satisfactory, as the bellows are subject to aging, leakage and other undesirable effects. Each such apparatus is disadvantageous to the small or low-volume user of such freeze drying or vacuum methods, in that the elaborate construction is overly expensive for such work. In addition, those who routinely stopper reference samples of a material being dried in large quantities have little use for such apparatus of large capacity and expense.
A more simplified arrangement is taught in U.S. Pat. No. 3,292,342, in which sample vials may be stoppered under refrigeration and vacuum through the reciprocal action of a push rod connected to a push plate disposed above the vials. Since the cylindrical sleeve within which the push rod reciprocates is metal and extends inside the freeze drying chamber, while being exposed to the air outside the chamber, various potential problems arise through the condensation of moisture on the cylindrical sleeve. Reciprocation of the rod is difficult to control, as the friction caused by the tight fit of the push rod, which was necessary to maintain the vacuum, made it extremely difficult to stopper a plurality of sample vials simultaneously. In addition, the integral use of refrigeration with such stoppering means as taught by each of the above references, imposes a minimum size and cost limitation which denies the use of these assemblies to the low-volume user.